Well I am new and I don’t have any ideas, I just asked him what will be the best platform to use for my properties site, as I told him that I need to handle lots more database, he suggested me to opt for asp.net, he feels mysql is not much safe and not efficient to handle such huge database

I wana know from this community which in these three will be best, or is there anything new? I need your valuable suggestion..

I would agree with the guy you spoke to, I would use asp.NET. You could also use classic asp, I suppose, but asp.NET is faster and more secure.
Basically it depends on personal preference. But if you want an objective and unbiased answer, search for feature comparisons between the three technologies.

For instance, PHP is open source software, so it's free to download, but asp.NET allows you to write code in multiple languages (and there's official documentation, online support forums, and all the server tools (minus the database engine) comes with Windows). You can also download an IDE (integrated development environment) for free from Microsoft at http://www.microsoft.com/express that installs the database engine for you.

I don't know much about Sharepoint, but I would recommend asp.NET over PHP, the code's easier to learn, and there's so much more help available if you get stuck on something.

Sharepoint is a huge asp.net framework for putting together massive connected systems across multiple domains in business networks. Its very powerful and very much overkill, and very expensive (developer wise).

I am a .NET architect and would agree with the choosing of asp.net, however I will say this. Choosing asp.net and sql server does not make your application better and more secure. You have to build it properly to ensure that. A PHP / mySQL site could be faster and secure than a poorly built asp.net website.

So "asp.net built well > php", but not built well you get no advantages.